Outdoor fan control system of air conditioner and control method thereof

ABSTRACT

An outdoor unit includes a pulse width modulation compressor, an outdoor heat exchanger. First and second outdoor fans are positioned near to the outdoor heat exchanger. The operation modes of the first and second outdoor fans are determined in accordance with the amount of refrigerant discharged from the compressor and external conditions. An outdoor temperature sensor is electrically connected to the input port of the outdoor control unit, and first and second outdoor fan operating units for respectively operating first and second outdoor fans are connected to the output port of the outdoor control unit. The outdoor control unit operates the first and second fans in a preset operation mode by confirming outdoor temperature data input from the outdoor temperature sensor and the loading time of the compressor and controlling the first and second outdoor fan operating units.

TECHNICAL FIELD

The present invention relates generally to air conditioners, and moreparticularly to a system and method for controlling the outdoor fan ofan air conditioner that employs a pulse width modulated compressor.

BACKGROUND ART

In an air conditioner, a condenser, that is, an outdoor side heatexchanger, is mounted on an outdoor unit, and serves to condenserefrigerant by heat transfer to its surroundings. In such a case, theamount of heat exchange in the outdoor side heat exchanger varies withthe rotational speed of a fan and an outdoor temperature. The variationin the amount of heat exchange directly affects the cooling capacity ofan indoor unit.

The difference between the temperatures of refrigerant and the outdoorair is large when the outdoor temperature is relatively low, so theamount of heat exchange in the outdoor side heat exchanger is increased.Consequently, there is a concern that the evaporation temperature ofrefrigerant in an evaporator, that is, an indoor side heat exchanger, isdecreased, and the surface of the indoor side heat exchanger may freeze.In such a case, the cooling capacity of the indoor unit is decreased.

On the other hand, the difference between the temperatures ofrefrigerant and the outdoor air is small when the outdoor temperature isrelatively high, so the amount of heat exchange in the outdoor side heatexchanger is decreased. Consequently, the evaporation temperature ofrefrigerant in the indoor side heat exchanger is increased, and theamount of heat exchange of refrigerant is decreased, so the coolingcapacity of the indoor unit is decreased.

Hence, in order to keep the cooling capacity of the indoor unit optimalregardless of outdoor temperature, it is necessary to properly regulatethe amount of heat exchange in the outdoor side heat exchanger accordingto variations in outdoor temperature.

To this end, in a conventional air conditioner, the rotational speed ofan outdoor fan is regulated to high speed or low speed according tooutdoor temperature. This regulation is performed for not only an airconditioner having a single outdoor fan but also an air conditionerhaving a plurality of outdoor fans. That is, when an outdoor temperatureis low, a plurality of outdoor fans are simultaneously operated at a lowspeed so as to reduce the amount of heat exchange in an outdoor sideheat exchanger; when an outdoor temperature is high, the outdoor fansare simultaneously operated at a high speed so as to increase the amountof heat exchange in the outdoor side heat exchanger.

However, the above-described conventional method for controlling theoutdoor fan of an air conditioner is problematic in that when the amountof compression and discharge of refrigerant varies with time as is thecase when an inverter compressor or a pulse width modulated compressoris used, the amount of heat exchange in an outdoor side heat exchangercannot be held constant because the outdoor fan is regulated based onlyon the outdoor temperature.

In particular, for a pulse width modulated compressor, the discharge ofrefrigerant is periodically or intermittently carried out during theoperation of the compressor. That is, a loading time, during whichrefrigerant is discharged, and an unloading time, during whichrefrigerant is not discharged are alternated, so the amounts ofcompression and discharge of refrigerant vary with time, thereby varyingthe amount of refrigerant flowing through an outdoor side heatexchanger. That is, when the loading time is relatively short, theamount of refrigerant flowing through the outdoor side heat exchanger isrelatively small. In this case, when the rotational speed of the outdoorfan is constant, a relatively excessive heat exchange is conducted inview of the amount of refrigerant flowing through the outdoor side heatexchanger. Accordingly, the cooling capacity of the indoor unit isincreased due to the supercooling of refrigerant in the outdoor heatexchanger. On the other hand, when the loading time is relatively long,the amount of refrigerant flowing through the outdoor side heatexchanger is relatively large. In this case, when the rotational speedof the outdoor fan is constant, a relatively insufficient heat exchangeis conducted in view of the amount of refrigerant flowing through theoutdoor side heat exchanger. Accordingly, the cooling capacity of theindoor unit is decreased due to an increase in the condensation pressureof refrigerant in the outdoor heat exchanger.

DISCLOSURE OF THE INVENTION

Accordingly, the present invention has been made keeping in mind theabove problems occurring in the prior art, and an object of the presentinvention is to provide a system and method for controlling the outdoorfan of an air conditioner employing an pulse width modulated compressor,in which the amount of heat exchange in the outdoor heat exchange of theair conditioner is properly regulated, thereby allowing the indoor unitof the air conditioner to have a proper cooling capacity.

In order to accomplish the above object, an aspect of the principles ofthe present invention, a system for controlling the outdoor fan of anair conditioner comprises a compressor in which the amount of dischargeof refrigerant is variable during its operation; an outdoor heatexchanger connected to said compressor; an outdoor fan(s) positionednear said outdoor heat exchanger; an outdoor temperature sensor forsensing outdoor temperature; and a control unit for controlling saidoutdoor fan(s) to be operated in one of preset operation modes accordingto an outdoor temperature sensed by said outdoor temperature sensor andthe amount of discharge of refrigerant of said compressor.

Further, according to another aspect of the principles of the presentinvention, a method for controlling the outdoor fan(s) of an airconditioner having a compressor controlled in a pulse width modulationmanner comprises detecting an outdoor temperature; detecting a loadingtime of said compressor; and operating said outdoor fan(s) in one ofpreset operation modes according to a detected outdoor temperature and adetected loading time of said compressor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the cycle of a system for controlling theoutdoor fans of an air conditioner in accordance with the presentinvention;

FIG. 2a is a sectional view showing a pulse width modulated compressorat a loading position, and FIG. 2b is a sectional view showing the pulsewidth modulated compressor at an unloading position;

FIG. 3 is a graph showing a relationship among the loading time and theunloading time and the amount of discharged refrigerant during theoperation of the compressor of FIGS. 2a and 2 b;

FIG. 4 is a block diagram showing the system for controlling the outdoorfans of an air conditioner in accordance with the present invention; and

FIG. 5 is a flowchart showing a method for controlling the outdoor fansof an air conditioner in accordance with the present invention.

*Description of reference characters of principal parts

 2: compressor  5: indoor heat exchanger  8: outdoor unit  9: indoorunit 26: pulse width modulated valve 27: outdoor control unit 28:outdoor communication circuit unit 29: indoor control unit 30: firstoutdoor fan 31: second outdoor fan 33: outdoor temperature sensor

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention are described indetail with reference to accompanying drawings.

FIG. 1 is a diagram showing the cycle of a system for controlling theoutdoor fans of an embodiment of the air conditioner in accordance withthe present invention. The air conditioner 1 includes a compressor 2, anoutdoor heat exchanger 3, a plurality of electronic expansion valves 4,and a plurality of indoor heat exchangers 5, which are connected to eachother by refrigerant conduits to form a closed refrigeration circuit. Ofthe refrigerant conduits, a refrigerant conduit connecting the outflowside of the compressor 2 to the inflow side of the electronic expansionvalves 4 is a high pressure conduit 6 for guiding the flow of highpressure refrigerant discharged from the compressor 2, while arefrigerant conduit connecting the outflow side of the electronicexpansion valves 4 to the inflow side of the compressor 2 is a lowpressure conduit 7 for guiding the flow of low pressure refrigerantexpanded in the electronic expansion valves 4. The outdoor heatexchanger 3 is situated on the high pressure conduit 6, while the indoorheat exchangers 5 are situated on the low pressure conduit 7. While thecompressor 2 is operated, refrigerant flows in the directions indicatedby solid arrows.

The air conditioner 1 of includes an outdoor unit 8 and a plurality ofindoor units 9. The outdoor unit 8 includes the above-describedcompressor 2 and the above-described outdoor heat exchanger 3. Theoutdoor unit 8 further includes an accumulator 10 situated on the lowpressure conduit 7 upstream of the compressor 2 and a receiver 11situated on the high pressure conduit 6 downstream of the outdoor heatexchanger 3. The accumulator 10 serves to collect and evaporate liquidrefrigerant having not been evaporated and allow evaporated refrigerantto flow into the compressor 2. If refrigerant is not evaporatedcompletely in the indoor heat exchangers 5, refrigerant entering theaccumulator 10 is a mixture of liquid refrigerant and gaseousrefrigerant. The accumulator 10 evaporates liquid refrigerant, andallows only gaseous refrigerant (refrigerant gas) to enter thecompressor 2. To this end, it is desirable to situate the entrance andexit ends of the refrigerant conduit situated inside of the accumulator10 in the upper portion of the accumulator 10.

Likewise, if refrigerant is not condensed completely in the outdoor heatexchanger 3, refrigerant entering the receiver 11 is a mixture of liquidrefrigerant and gaseous refrigerant. The receiver 11 is constructed toseparate the liquid refrigerant and the gaseous refrigerant from eachother and to allow only the liquid refrigerant to be discharged. To thisend, the entrance and exit ends of the refrigerant conduit situatedinside of the receiver 11 are extended to the lower portion of thereceiver 11.

In order to bypass gaseous refrigerant situated in the receiver 11, avent bypass conduit 12 is provided to connect the receiver 11 to the lowpressure conduit 7 upstream of the accumulator 10. The entrance end ofthe vent bypass conduit 12 is situated in the upper portion of thereceiver 11, so only gaseous refrigerant enters the vent bypass conduit12. A vent valve 13 is provided on the vent bypass conduit 12 andcontrols the flow rate of gaseous refrigerant bypassed. Accordingly, thegaseous refrigerant collected in the receiver 11 flows in the directionsof double dotted arrows by the action of the vent valve 13.

The portion of the high pressure conduit 6 extended from the receiver 11is constructed to pass through the accumulator 10. This construction isto evaporate the liquid refrigerant of low temperature collected in theaccumulator 10 by using the refrigerant of relatively high temperaturepassing through the high pressure conduit 6. In order to effectivelyevaporate the refrigerant, the portion of the low pressure conduit 7situated in the accumulator 10 is formed in the shape of U, while theportion of the high pressure conduit 6 passing through the accumulator10 is positioned to pass through the interior of the U-shaped portion ofthe low pressure conduit 7.

The outdoor unit 8 further includes a hot gas bypass conduit 14connecting the portion of the high pressure conduit 6 between thecompressor 2 and the outdoor heat exchanger 3 to the accumulator 10, anda liquid bypass conduit 15 connecting the downstream side of thereceiver 11 and the upstream side of the accumulator 10. A hot gas valve16 is situated on the hot gas bypass conduit 16 to control the flow rateof hot gas bypassed, and a liquid valve 17 is situated on the liquidbypass conduit 15 to control the flow rate of liquid refrigerantbypassed. Accordingly, when the hot gas valve 16 is opened, a portion ofhot gas discharged from the compressor 2 flows along the hot gas bypassconduit 14 in the direction indicated by the dotted arrow of FIG. 1;when the liquid valve 17 is opened, a portion of liquid refrigerantdischarged from the receiver 11 flows along the liquid bypass conduit 15in the direction indicated by the double dotted arrow of FIG. 1.

The outdoor unit 8 further includes first and second outdoor fans 30 and31 positioned near the outdoor heat exchanger 3. The first and secondoutdoor fans 30 and 31 are positioned side by side and allow externalair to pass through the outdoor heat exchanger 3, so heat exchange canoccur in the outdoor heat exchanger 3. The operation mode of the firstand second outdoor fans 30 and 31 are determined according to the amountof refrigerant discharged from the compressor 2 and external conditionsas will be described in more detail later. Additionally, the outdoorunit 8 further includes an outdoor temperature sensor 33 for measuringoutdoor temperature.

A plurality of indoor units 9 are arranged in parallel. Each of theindoor units 9 includes an electronic expansion valve 4 and an indoorheat exchanger 5. Consequently, a plurality of indoor units 9 areconnected to a single outdoor unit 8. The capacities and shapes ofindoor units may be identical with or different from one another.

As depicted in FIGS. 2a and 2 b, a variable capacity compressorcontrolled in a pulse width modulation manner is employed as acompressor 2. The compressor 2 includes a casing 20 provided with aninlet 18 and an outlet 19, a motor 21 situated in the casing 20, arotating scroll 22 rotated by the rotating force of the motor 21, and astationary scroll 24 defining a compressing chamber 23 together with therotating scroll 22. A bypass conduit 25 is attached to the casing 20 toconnect a position over the stationary scroll 24 to the inlet 18, and aPWM valve (Pulse Width Modulated Valve) 26 in the form of a solenoidvalve is mounted on the bypass conduit 25. In FIG. 2a, the PWM valve 26is OFF and closes the bypass conduit 25. In this state, the compressor 2discharges refrigerant. This state is referred to as “a loading state”,and in this state the compressor 2 is operated at 100% capacity. In FIG.2b, the PWM valve 26 is ON and opens the bypass conduit 25. In thisstate, the compressor 2 does not discharge refrigerant. This state isreferred to as “an unloading state”, and in this state the compressor 2is operated at 0% capacity. Power is supplied to the compressor 2regardless of the loading and unloading states, and the motor 21 isrotated at a constant speed. When power is not supplied to thecompressor 2, the motor 21 is not rotated and the compressor 2 is notoperated.

As shown in FIG. 3, the compressor 2 periodically undergoes the loadingand unloading states during its operation. The loading time and theunloading time vary according to required cooling capacity. During theloading time the temperature of the indoor heat exchanger 5 is decreasedbecause the compressor 2 discharges refrigerant, while during theunloading time the temperature of the indoor heat exchanger 5 isincreased because the compressor 2 does not discharge refrigerant. InFIG. 3, the hatched portions indicate the amount of dischargedrefrigerant. A signal for controlling the loading time and the unloadingtime is referred to as a duty control signal. In an embodiments of thepresent invention, the capacity of the compressor 2 is varied in such away that the loading time and the unloading time are varied according tothe required total cooling capacity of the compressor 2 while each cycleperiod is kept constant, for example, at twenty seconds.

FIG. 4 is a block diagram showing the system for controlling the outdoorfans of an air conditioner in accordance with the present invention. Asillustrated in FIG. 4, the outdoor unit 8 includes an outdoor controlunit 27 that is connected to, and controls the compressor 2 and the PWMvalve 26. The outdoor control unit 27 is connected to an outdoorcommunication circuit unit 28 to transmit and receive data.Additionally, an outdoor temperature sensor 33 is connected to the inputport of the outdoor control unit 27, and first and second outdoor fanoperating units 34 and 35 for operating first and second outdoor fans 30and 31 respectively, are connected to the output port of the outdoorcontrol unit 27. The outdoor control unit 27 operates the first andsecond fans 30 and 31 in a preset operation mode by confirming outdoortemperature data inputted from the outdoor temperature sensor 33 and theloading time of the compressor 2, and by controlling the first andsecond outdoor fan operating units 34 and 35.

Each of the indoor units 9 includes an indoor communication circuit unit32 connected to an indoor control unit 29 and the outdoor unit 8 totransmit and receive data. The outdoor communication circuit unit 28 andthe indoor communication circuit unit 32 may be constructed to transmitand receive data in a wire or wireless fashion. A temperature detectingunit 30 and a temperature setting unit 31 are connected to the inputport of the indoor control unit 29, and the electronic expansion valve 4is connected to the output port of the indoor control unit 29. Thetemperature detecting unit 30 is a temperature sensor for sensing thetemperature of a room to be air-conditioned. The indoor control unit 29receives signals from the temperature detecting unit 30 and thetemperature setting unit 31 and calculates the required cooling capacityof the indoor unit 9 on the basis of the difference between an indoortemperature and a set temperature. The loading time of the compressor 2is determined according to the required cooling capacity calculated bythe above-described way.

The first and second outdoor fans 30 and 31 each have three operationmodes of stop, low speed and high speed modes. Exemplary operation modesdetermined by the combination of the two outdoor fans 30 and 31 areshown in the following table.

TABLE 1 Mode First outdoor fan Second outdoor fan 5 high speed highspeed 4 low speed high speed 3 low speed low speed 2 stop high speed 1stop low speed 0 stop stop

That is, the number of operation modes determined by the combination oftwo outdoor fans are six. Although two fans are utilized in thisembodiment, only one fan can be utilized. In such a case, the operationmodes of the fan may be three of stop, low speed and high speed modes.It should be understood and readily apparent to those skilled in the artthat any number of fans, and any number of operation modes thereof maybe possible.

In an embodiment, the operation modes are predetermined an outdoortemperature and the loading time of the compressor 2. Table 2 shows anexemplary operation modes according to an outdoor temperature and aloading time when a duty cycle control period for a compressor of 7.5horsepower is twenty seconds.

TABLE 2 Outdoor temperature 28° C. 7° C. or 8 to 13 to 18 to 23 to orlower 12° C. 17° C. 22° C. 27° C. higher Load- 10 0 2 3 4 5 5 ingseconds time or more 5 to 9 0 1 2 3 4 5 seconds 4 0 0 1 2 3 5 seconds orless

As apparent from Table 2, as the outdoor temperature becomes higher andthe loading time of the compressor 2 becomes longer (as the loading timeof the compressor 2 is longer, the amount of discharge of refrigerantbecomes larger), the operation modes are preset to allow the rotationalspeed of the first and second outdoor fans 30 and 31 to become higher.

Referring to FIG. 5, a method for controlling the outdoor fans of an airconditioner is described. First, when the compressor 2 is started, theoutdoor control unit 27 receives an outdoor temperature and the loadingtime of the compressor 2 (S101). The outdoor temperature sensor 33detects an outdoor temperature, and the outdoor control unit 27 hasinformation on the loading time of the compressor 2 when the compressor2 is operated. Thereafter, an operation mode is selected according tothe outdoor temperature and the loading time of the compressor (S102).The selection of the operation mode is made from a plurality ofoperation modes, e.g., from the six modes shown in Table 1 and 2.

Next, prior to the performance of a selected operation mode, it isdetermined whether the first and second outdoor fans 30 and 31 arestopped (S103). In a preferred embodiment, when the first and secondoutdoor fans 30 and 31 are stopped, the fans 30 and 31 are operated at ahigh speed regardless of the selected operation mode (S104). That is,when the first and second outdoor fans 30 and 31 are all stopped, thefans 30 and 31 are operated in the mode 5. This is to enhance thestarting power of an outdoor fan operating motor. Such operation iscontinued for two to five seconds (preferably, for three seconds).

If it is determined that the outdoor fans 30 and 31 are not stopped atSTEP S103, or after the operation of the outdoor fans 30 and 31 exceedsthree seconds at STEP S104, the outdoor fans 30 and 31 are operated inthe operation mode selected at STEP S102 (S105). For example, if theoutdoor temperature is lower than 7° C., the mode 0 is selectedregardless of the loading time of the compressor 2. In the mode 0, thefirst and second outdoor fans are all stopped. In this state, if theoutdoor temperature is 15° C. and the loading time of the compressor 2is 12 seconds, the mode 3 is selected as the operation mode according toTable 2. However, the first and second outdoor fans 30 and 31 are notoperated directly in the mode 3, but they are operated in the selectedmode 3 after being operated in the mode 5 for three seconds. As aresult, the operation modes of the first and second outdoor fans 30 and31 are all changed from a high speed mode to a low speed mode.

INDUSTRIAL APPLICABILITY

As described above, the present invention provides a system and methodfor controlling the outdoor fan of an air conditioner, in which theoutdoor fan is controlled according to the loading time of a pulse widthmodulated compressor and an outdoor temperature, thereby properlyregulating the amount of heat exchange in the outdoor heat exchanger ofthe air conditioner and, accordingly, allowing the indoor unit of theair conditioner to have a proper cooling capacity.

What is claimed is:
 1. A method of controlling at least one outdoor fanof an air conditioner having a compressor controlled in a pulse widthmodulation, comprising: detecting an outdoor temperature; detecting aloading time of said compressor; and operating said at least one outdoorfan in one of preset operation modes according to said detected outdoortemperature and said detected loading time of said compressor.
 2. Themethod according to claim 1, wherein as said outdoor temperature becomeshigher and said loading time of said compressor becomes longer, saidselected one of said preset operation modes allowing the rotationalspeed of said outdoor fan to become higher.
 3. The method according toclaim 2, wherein the operation modes of said at least one outdoor faninclude stop, low speed and high speed modes, and said at least oneoutdoor fan is operated in selected one of said preset operation modesafter having been operated in the high speed mode for a predeterminedtime when said at least one outdoor fan is changed from the stop mode toanother operation mode.
 4. The method according to claim 3, wherein saidpredetermined time is two to five seconds.
 5. The method according toclaim 1, wherein said at least one outdoor fan comprises two outdoorfans each having stop, low speed and high speed operation modes, andsaid operation modes for said two outdoor fans include six of stop-stop,stop-low speed, stop-high speed, low speed-low speed, low speed-highspeed and high speed-high speed operation modes.
 6. A system to controlat least one outdoor fan of an air conditioner, comprising: a compressorin which an amount of discharge of refrigerant is variable during itsoperation; an outdoor heat exchanger connected to said compressor; oneor more outdoor fans positioned near said outdoor heat exchanger; anoutdoor temperature sensor to sense an outdoor temperature; and acontrol unit to control said at least one outdoor fan to be operated inone of preset operation modes according to said sensed outdoortemperature and said amount of discharge of refrigerant of saidcompressor, wherein, as said outdoor temperature becomes higher and aloading time of said compressor becomes longer, said selected one ofsaid preset operation modes allowing the rotational speed of saidoutdoor fan to become higher.
 7. The system according to claim 6,wherein said at least one outdoor fan comprises one outdoor fan, andsaid preset operation modes include stop, low speed and high speedmodes.
 8. The system according to claim 6, wherein said at leastone-outdoor fan comprises two outdoor fans each having stop, low speedand high speed operation modes, and said preset operation modes for saidtwo outdoor fans include stop-stop stop-low speed, stop-high speed, lowspeed-low speed, low speed-high speed and high speed-high speedoperation modes.
 9. The system according to claim 6, wherein saidcompressor and said outdoor heat exchanger constitute an outdoor unit,and said air conditioner further comprises at least one indoor unithaving an electronic expansion valve and an indoor heat exchanger.
 10. Asystem to control at least one outdoor fan of an air conditioner,comprising: a compressor in which an amount of discharge of refrigerantis variable during its operation; an outdoor heat exchanger connected tosaid compressor; one or more outdoor fans positioned near said outdoorheat exchanger; an outdoor temperature sensor to sense an outdoortemperature; and a control unit to control said at least one outdoor fanto be operated in one of preset operation modes according to said sensedoutdoor temperature and said amount of discharge of refrigerant of saidcompressor, wherein, said compressor is controlled in a pulse widthmodulation manner and the amount of discharge of refrigerant of saidcompressor is determined by a loading time of said compressor.